People's Pharmacy: Old study revives butter versus margarine debate

Updated 3:12 pm, Sunday, February 24, 2013

Ginger salmon filets carry healthful omega-3 fats. Salmon and other seafood are a good source of omega-3 fats.

Ginger salmon filets carry healthful omega-3 fats. Salmon and other seafood are a good source of omega-3 fats.

Photo: James F. Quinn / Chicago Tribune

People's Pharmacy: Old study revives butter versus margarine debate

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Ask anyone what makes a diet heart-healthy, and you are likely to hear about substituting vegetable oils for butter, lard and other saturated fats. The American Heart Association recommends omega-6 fatty acids from corn, safflower, soy or sunflower oils.

A new study turns this conventional wisdom on its head. Actually, the study is more than 30 years old. But the data have just been recovered and reanalyzed. And the results are nothing short of shocking.

The Sydney Diet Heart Study was conducted in Australia between 1966 and 1973. The scientists recruited 458 men who had recently had a coronary event. (This put them at high risk for a second heart attack.)

Half the men carried on with their usual diet containing saturated fat during the study, while the other half were given safflower oil and margarine made of safflower oil to use instead of butter. The expectation was that the polyunsaturated fats (PUFAs) in safflower oil would help lower cholesterol and ward off second heart attacks.

The data were partially analyzed and published, but key questions were never answered. Apparently the researchers ran out of money, and the data languished in a box in a Sydney garage for decades. These numbers have now been resurrected, reanalyzed and published in the journal BMJ (online, Feb. 5, 2013). The results challenge conventional beliefs about a heart-healthy diet.

Even though the men consuming omega-6 PUFAs such as linoleic acid did lower their cholesterol as the investigators had hoped, this did not save their lives. The men who had been provided with safflower oil were 60 percent more likely to die during the study (17.6 percent of them died compared with 11.8 percent of the men on their usual unsupervised diets). In addition, they were 75 percent more likely to die of coronary heart disease (16.3 percent of the men on the PUFA-rich diet compared with 10.1 percent of the men eating butter and other saturated fats).

This long-forgotten study throws the traditional diet-heart hypothesis into question. It and two other randomized controlled trials have demonstrated that diets high in omega-6 fatty acids found in safflower and corn oil may actually increase the risk of heart disease and death, the opposite of what was expected.

The scientists speculate that when breakdown products of linoleic acid are oxidized, they form nasty compounds that may clog coronary arteries. This is especially true for people who smoke or drink, exposing their bodies to excessive oxidative stress and even greater risk.

To make sense of these results, keep in mind that safflower oil has almost no omega-3 fatty acids. It may very well be the imbalance between these two types of PUFAs that caused the unanticipated heart attacks. The investigators note that in studies that included omega-3 fats along with linoleic acid, heart-attack deaths dropped.

Where can you get more omega-3 fats in your diet? Fish and shellfish are rich in these fatty acids. Other sources include walnuts, almonds, pecans and pistachios.

Including more monounsaturated fats also is good for heart health. Using olive oil instead of vegetable oil and enjoying an occasional avocado are tasty ways to do this.